Zelretch shook his head, "If it were just that, I wouldn't be too concerned. I'd simply observe the civilization of that parallel world crumble from a distance. The issue is that my magic disrupted the boundary between that parallel world and ours!"

Shirou furrowed his brows...

"Do you understand the concept of parallel worlds, Eternal King?"

"In a broader sense, it refers to the multiple universes contained within the multiverse."

"You can think of it that way. But to be more precise, two parallel worlds are like the front and back sides of a blank piece of paper."

Zelretch picked up a blank sheet of paper and continued, "Let's imagine that this world we're in right now is the front side of the paper, while the parallel world of that girl is the back side. Whatever is drawn on the front side of this blank paper cannot cross over to the back side, and vice versa. The line that separates the front and back sides of this paper represents the boundary between parallel worlds."

Shirou furrowed his brow, "So, in this analogy, you're suggesting that your magic destroyed the line that separates the front and back sides of the paper, essentially connecting this world and the parallel world?"

Zelretch nodded gravely, "Originally, aside from the entities who attained the truth of the world, my magic was the sole means of freely traversing between parallel worlds. However, due to the rampage of my magic over 1,500 years ago, the boundary lines between the two worlds were shattered, creating a link between them. That's why the gods from that world can come to ours, and why that little girl can travel between the two worlds."

"I thought it was the Holy Grail..."

"No, the Holy Grail doesn't have that kind of power. Only my magic can truly mess with parallel worlds, aside from those entities, of course!"

He added, "Due to the rampage of my magic, a connection was formed between two parallel worlds, letting people from that world, even gods, to enter this world."

"An invasion from parallel worlds..." Shirou said, "But how does all of this connect to the 'resurgence of the Age of Gods' you mentioned earlier?"

"About 1,500 years ago, I accidentally destroyed the boundary that separated the two parallel worlds. Back then, this world was at the end of the Age of Gods, while the other world was still under the rule of the gods."

"Are you saying...!" Shirou's eyes widened in sudden realization.

He had a chilling suspicion.

"Exactly," Zelretch nodded and explained, "When the boundary lines were destroyed, it caused a breach that allowed the Age of Gods from that world to flow into ours! Therefore, the Age of Gods in their world came to an abrupt end, while our world, which had already concluded its Age of Gods, began showing signs of resurgence."

Shirou raised an important question, "But if over 1,500 years have passed in this world since the end of that war, wouldn't the Age of Gods have already resurged here? Why did the signs of resurgence only appear when I returned from that specific time point?"

"That's due to the gap in the boundary lines. I closely observed it, and initially, the gap was small. However, for some reason, it has now become enormous. The Age of Gods from that world is pouring into ours relentlessly, and even the gods themselves have started manifesting here. And based on this understanding, those gods from that world are undoubtedly..."

"Invaders!" Shirou rubbed his temples with a troubled expression.

At first, he figured that acquiring the Class Cards in Fuyuki City was just a minor event, but little did he know it was actually linked to the resurgence of the Age of Gods. He found that troublesome on its own, but what caught him completely off guard was the revelation that this incident was an invasion from parallel worlds!

And to make matters even worse, the invaders weren't humans, but actual gods!

"Is there a way to repair that breach?"

"That's exactly what I wanted to discuss with you. Unfortunately, I cannot directly intervene in this incident."

Shirou furrowed his brow, "So, you're putting your efforts into fixing the breach in the boundary?"

Zelretch snorted, neither explicitly confirming nor denying it.

"Wait, so you're saying I'm the one who has to handle those invaders from the other world?"

Zelretch nodded.

"If that's the case, why don't you just take me directly to that world?"

"That's not possible. Interfering with that world again would only worsen the breach in the boundary. If you wish to go there, it's better to return to Fuyuki City and use the gateway there."

"I don't understand. It just doesn't make sense to me. If Fuyuki City is supposed to be the gateway to another world, why haven't I ever seen a single god crossing over during all my time there? Instead, I saw one in London! It goes against all logical reasoning!"

"Well, those gods you met in London managed to breach the boundaries between the worlds. However, the connection point in Fuyuki City was deliberately opened by magi from that world who used the Holy Grail as a means to fulfill their wishes. It is highly probable that in the future, we will witness many people from that world coming through that very connection point. Therefore, it is essential that someone guards the connection point in Fuyuki City, whether it's for defending our world or going into theirs. Moreover, when that girl arrived, some of the Class Cards had already found their way into Fuyuki City through the connection point!"

"If you were able to bring that girl here, why didn't you also bring the Class Cards?"

Zelretch's expression turned disdainful as he sneered, "Oh, please. Don't mistake me for some hero of justice."

Shirou couldn't resist mocking him, "If you're not a hero of justice, why bother getting involved in this incident?"

His reply was calm and deliberate, "I'm simply trying to make up for my own mistakes."

As if on cue, a fissure materialized behind Zelretch, and he began to slowly sink into it. He added, "I need to go and fix the breach in the boundary. That girl has great potential as a Magical Girl, but I don't have the energy to handle her properly at the moment. So, I'll leave her in your capable hands, Eternal King. After all, you're her brother from a parallel world."

Shirou sighed, "We may be parallel world counterparts, but we are not the same person, and certainly not the same soul."

Finally, the situation became clear, and its true nature was revealed as an invasion from parallel worlds! The one responsible for this incident was none other than Zelretch and his battle against Crimson Moon.

Considering that Fuyuki City acted as a gateway between these two worlds, it desperately needed defenders, especially because it was Shirou's hometown.

He couldn't help but sigh at the realization. Fuyuki City had undoubtedly faced numerous disasters and hardships over time.

On top of that, Fuyuki City had also been a battleground for the Holy Grail Wars throughout the years. Not to mention the attack it suffered from the Dead Apostle Ancestor, Forest of Einashe, nine years ago. And now, to add to its list of troubles, it had become a crucial nexus linking two parallel worlds.

It was undoubtedly a city plagued with troubles!

The solution to this incident seemed straightforward—protect Fuyuki City and await Zelretch's restoration of the boundaries between the parallel worlds.

However, he couldn't shake off the feeling that there was more to this than met the eye.

Setting aside all other concerns, the revival of the Age of Gods triggered by the invasion of the parallel worlds raised perplexing questions. Why did the gods choose to descend on the British Isles? And why did the signs of the Age of Gods' resurgence only occur in that region?

It was a question that lingered in his mind—one that Zelretch had briefly mentioned but never fully explained.

Moreover, the most crucial aspect was that the breach had occurred over 1,500 years ago. Why had there been no indications of revival until now? What had triggered the sudden emergence of these signs?

Equally significant was the mysterious reason Zelretch mentioned, one that contributed to the expansion of the breached boundary. This was the aspect that concerned Shirou the most.

He couldn't help but wonder about the unknown factor that played a significant role in this incident.

...

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